Electric switch



Aug. 4, 1942. o. L. TAYLOR ELECTRIC SWITCH Filed July 19, 1940 Insulation flay/refit Mater/a1 Insulation Fig.2

Llllll INVENTOR Owen L. Taylor.

Patented Aug. 4, 1942 UNITED STATES PATENT OFFICE ELECTRIC SWITCH Owen L. Taylor, Forest Hills, Pa., assignor to Westinghouse Electric & Manufacturing (10mpany, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 19, 1540, Serial No. 346,311

Claims. (01. 200 -147) .type failure to ground or across the line may occur because the arc is not extinguished quickly enough. Also, beading of the contact members may occur, wherein the contact material is melted and forms a small ball or bead which may become of such a size as to prevent the proper operation of the switch.

An object of my invention, generally stated, is to provide a switch of the knife-blade type which shall be simple and efiicient in operation and which may be economically manufactured and installed. 3-,

A more specific object of myjinvention is to extinguish quickly the arc drawn between the contact members of a knife-blade switch.

Another object of my invention is to prevent the are from grounding through the housing of an enclosed electric switch.

A further object of my invention is to prevent beading of the contact members of a knife-blade switch.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with my invention, a number of straps, composed of steel or other magnetic material, are so mounted on a fiber plate that they move through the field of the are drawn between the moving switch blade and the stationary contact member, thereby drawing the arc towards the steel straps and their fiber support to break it up into small arcs. Beading is prevented by rapidly extinguishing the arc and moving the arc, across the stationary contact blade upon opening the switch.

For a fuller understanding of the nature and objects of my invention reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure l is aview partially in side elevation and partially in section of a knife-blade switch embodying my invention and enclosed in a sheet metal cabinet; I

Fig. 2 is a view, partially in end elevation and partially in section, of the switch and cabinet shown in Fig. 1; and

Fig. 3 is a view, in perspective, of a portion of the switch structure shown in Figs. 1 and 2,

shown therein comprises a. metal housing I0 having a cover II which may be hinged to the housing in the usual manner. An insulating switch block I2 is secured to the bottom of the housing ID for supporting the electrical members of the switch structure and insulating them from the housing. Sincethe switch illustrated is of the two pole type, two sets of electrical members are supplied, as illustrated in Fig. 2. However,

since both poles are similar in construction, only one pole will be described in detail.

As shown in Fig. l, fuse clips I3 for supportin a cartridge fuse I4 are secured to the top of the switch base I2. A stationary contact member I5 is also secured to the switch base I2. Likewise, a hinge jaw I6 is secured to the base I2 in the usual manner.

As shown in Fig. 3, a switch member comprising a pair of blades I! which are secured together by rivets I8 is pivotally mounted on the hinge jaw I6 by means of a rivet I9. As shown in Fig. 2, the ends of the switch blades I'I op- Referring to the drawing, the enclosed switch posite the hinge jaw I6 are spaced apart to engage opposite faces of the stationary contact member I5.

In accordance with a well known practice in switches of the present type, the switch blades II are provided with an insulating operating arm 2I that is secured to the blades by the rivets I8 and spaced from the 'blades by a spacing member 22. A notch 23 is provided in the operating arm 2I for receiving an operating bail 24 that is journaled in the side walls of the housing III. The operating bail 24 is provided with an integral operating handle 25 that extends exteriorly of the housing. In this manner the switch blades I! may be actuated about the pivot point I9 to disengage the stationary contact member I5.

In order to reduce the overall dimensions of switches of the present type, the side walls of the housing are necessarily disposed relatively close to the contact members of the switch. Consequently, it has been found that under certain conditions of operation the are drawn between the stationary contact member I5 and the movable switch members Il may jump across the space between the switch members and the side wall of the housing which is usually grounded. When the arc grounds through the switch housing, it endures until the circuit is interrupted by the fuse, thereby destroying the contact members by the excessive heat of the arc.

In order to prevent the foregoing condition, it has previously been proposed to provide a barrier between the contact members of the switch and the side wall of the housing, and such barriers have been utilized in enclosed switches of the type herein illustrated. In the present structure the bottom of the insulating operating member 2| is extended a suiiicient distance below the switch members I? to provide a barrier between the contact member i5 and the side walls of the housing l when the switch is in its fully opened position. Therefore, the member 2| functions as a barrier to prevent the are from jumping to the adjacent side wall of the switch housing.

With a view to extinguishing the are more quickly than in previously known switches of the present type and to preventing the are from jumping from one pole of the switch to another pole of opposite polarity, and also to preventing beading of the contact members of the switch, I have provided an arc controlling or dissipating means in the form of a plurality of straps 2| which are mounted on the insulating member 2| in spaced relation. The straps 26 may be composed of steel or other suitable material having a relatively low magneticretentivity and may be attached to the member 2| in any suitable manner. In the present structure the member 2| is provided with holes 21 through which the ends of the straps 26 are inserted and then bent over to secure the straps on the member 2|. Thus it will be seen that the straps 26 are carried by the member 2| through the field of the arc stream in a plane parallel to the arc drawn between the switch member I1 and the stationary member I1 and the stationary contact member of the switch member I! and the stationary contact member l5 of the switch structure. It is to be understood that any other'suitable arrangement may be used in place of the straps 28 so long as it functions to produce the same result.

The presence of the magnetic steel straps weakens a portion of the magnetic field of the arc stream and draws the are against these straps and their fiber support 2|. The position of the arc is thus determined and no other confinement is necessary to prevent flashover between the opposite poles of the switch. The arc striking the fiber support releases gaseswhich are an aid in extinguishing the arc. Furthermore, when the arc strikes the steel straps, it is broken up into a plurality of small arcs, thereby further aiding in extinguishing the arc.

The beading of the contact members is prevented by the quick extinction of the arc and by rapidly moving the arc across the contact blade l5 upon opening the switch. In previous switches an arc was usually drawn at a certain point on the contact member and continued to remain at this point until extinction. In such a structure the heat of the arc is concentrated upon a single point and tends to melt the contact metal. A cumulative process occurs which builds up a bubble of metal that may reach such proportions as to prevent closure of the switch.

In order to prevent the foregoing beading action in the present switch, the arc is always drawn at the point A and then rapidly swept across the length of the contact tipto the point B, as shown in Fig. 1. This is accomplished by so constructing the switch that the last point in contact and, therefore, the initial arcing point is always the same, and then sweeping the are over the contact by electrical and magnetic means coupled with the movement of the switch blade and the flber member which supports the magnetic straps 26.

From an analysis of the electrical forces involved, coupled with the movement of the switch blade and the steel straps, it will be seen that the current which is induced in the steel straps moving in the field of the are stream produces a magnetic field which so reacts on the arc stream that the arc is driven across the surface of the contact member l5 while the switch is being opened. It will be noted that the straps 26 are disposed on the fiber support 25 at such an angle that they successively enter the field of the are at substantially the same position during the opening of the switch, thereby producing the desired sweeping action on the arc. Furthermore, the magnetic members 26 are so positioned on the fiber barrier 2| that the arc is extinguished by the time the switch is fully opened.

As explained hereinbefore, the other pole of the switch is similar in structure and functions in the same manner as the one herein described. Therefore, it is apparent that I have provided an enclosed switch structure which prevents grounding of the arc during the opening-of the contact members of the switch and also prevents fiashover between opposite poles of the switch. Furthermore, beading of the contact members is reduced by the sweeping action of the magnetic field of the current induced in the magnetic members provided in the present structure.

In this manner I have provided an enclosed switch which is simple in structure, eflicient in operation and which may be economically manufactured. Furthermore, actual tests have proven that the rating of a switch constructed as herein described may be increased without increasing its dimensions over prior switches.

Since numerous changes may be made in the above described construction and difierent embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. An electric switch of the knife blade type comprising a contact member of a predetermined width, a pivotally mounted switch member for e g and disengaging the contact member at a predetermined point, an insulating member disposed adjacent the contact member and movable with the switch member, and a plurality of elongated spaced'magnetic members carried by the insulating member and movable past the contact member in a plane parallel to the surface of the contact member engaged by the switch member said magnetic members having a length substantially equal to the width of said contact member to sweep the arc from said point of disengagement across the knife edge of the contact member when disengaged from the switch member.

2. An electric switch of the knife blade type comprising a contact member of a predetermined width, a pivotally mounted switch blade for engaging and disengaging the contact member at a predetermined point, an insulating member disposed adjacent the contact member and movable with the switch blade, and a plurality of elongated spaced magnetic members carried by the insulating member and movable in a plane parallel to the are drawn between the contact member and the switch blade when they are separated said magnetic members having a length substantially equal to or greater than the width of said contact member and disposed substantially parallel to said switch blade to sweep the arc from said pointof disengagement across the knife edge of said contact member.

3. In an enclosed switch of the knife blade type, in combination, a housing, an insulating base therein, a contact member of a predetermined width mounted on the base, an angularly movable switch member for engaging and disengaging the contact member at a predetermined point, thereby drawing an arc at said point, a combined barrier and operating member for the switch member, said barrier being disposed between the contact member and a wall of the housing, and a plurality of elongated magnetic members disposed on said barrier in spaced relation, the length of said magnetic members being substantially equal to the width of said contact member, said magnetic members being moved at the side of the arc stream to sweep the are from said point of disengagement across the knife edge of said contact member.

4. In an enclosed switch of the knife blade type, in combination, a housing, an insulating base therein, a contact member of a predetermined width mounted on the base, an angularly movable switchmember for engaging and disengaging the contact member at a predetermined point, thereby drawing an arc at said point, a combined barrier and operating member for the switch member, said barrier being disposed between the contact member and a wall of the housing, and a plurality of elongated magnetic members disposed on said barrier in spaced relation, the length of said magnetic members being substantially equal to or greater thanthe width of said contact member, said magnetic members being carried past the contact member by said barrier to sweep the are from said point of disengagement across the knife edge of said contact member.

5. In an enclosed switch of the knife blade type, in combination, a housing, an insulating base therein, a contact member mounted on the base, said contact member having a predetermined width, a pivotally mounted switch member for engaging and disengaging the contact member at a predetermined point, a combined barrier and operatingmember for the switch member, said barrier being disposed between the contact member and a wall of the housing, and a plurality of magnetic straps disposed on said barrier in spaced relation, the length of-said straps being substantially equal to the width oi said contact member, said magnetic straps being moved successively into the magnetic field of the are drawn between the contact member and the switch member at said point of disengagement when they are separated, thereby sweeping the arc across the knife edge of the'contact member.

OWEN L. TAYLOR. 

